The present invention is directed to a blood aspirator that reduces the intake of air bubbles during aspiration of blood to reduce damage to the aspirated blood due to aspiration of the bubbles.
Vacuum-operated blood aspirators are conventional devices which are used in certain cases to remove blood from a patient, such as during a surgical procedure. The removed blood may be reinfused back into the patient at substantially the same time as it is removed to eliminate the need to obtain blood from an alternative blood source. Although re-use of vacuum-aspirated blood is generally advantageous, it has been recognized that aspiration may damage the blood due to air bubbles entrained in the aspirated blood. For example, in an article entitled "A Low-Hemolysis Blood Aspirator Conserves Blood During Surgery," Clague, et al. state that "Blood damage caused by traditional vacuum-operated suction tubes, particularly when air is aspirated along with the blood, usually exceeds damage from all other components. In addition to platelet injury, there is a high degree of hemolysis, which leads to high plasma hemoglobin levels and reduces the number of red blood cells available for reinfusion during cases of blood conservation, such as autologous transfusion and cardiac bypass."
U.S. Pat. No. 4,976,682 to Lane, et al. discloses a blood recovery system that reduces blood damage by minimizing the intake of air bubbles in the aspirated blood. The Lane, et al. blood recovery system includes a suction pump for aspirating blood and a bubble detector for detecting the presence of bubbles in the aspirated blood. As described in column 13, lines 34-42 of the Lane, et al. patent, as soon as a bubble is detected within the suction tip at the bubble detector, the speed of the suction pump is reduced. The pump speed continues to be reduced until no air is detected by the bubble detector. When the vacuum pump slows to the point where no air is detected by the bubble detector, the suction pump speeds up slightly until a small bubble appears at the suction tip, at which time the pump again slows.